So if I'm not mistaken the salaries of Stoll (it's still listed as tentative), O'Sullivan, Richardson, and the 7th defenseman have a cushion of $8,787,500 to fit under if 40 million is an internal hard cap that can't be exceeded.

Correct.....And Stoll's contract is rumored to be front loaded. So he would probably make at least $4 million this season. That would leave about $4.8 million for O'Sullivan, Richardson and another defenseman. Let's assume for a moment that O'Sullivan gets about $3.5 million and Richardson gets about $750,000. The would only leave about $550,000 for a veteran defenseman. That will not really get anyone of value. So somebody will have to be traded to make room for the 7th defenseman coming in.